Roller earth-boring drill cutter



Feb. 12 1924. 7 1,483,487

F. L. SCOTT ROLLER EARTH BORING DRILL CUTTER Filed April 10, 1923attozweg Patented'Feb. 12, 1924.

V 1,483,487 PATENT OFFICE.

FLOYD L. SCOTT, OF HOUSTON, TEXAS.

ROLLER EARTH-BORING DRILL CUTTER.

Application filed April 10, 1923. Serial No. 631,112.

To all whom it may concern:

Be it known that I, FLOYD L. Scorn-a citizen of the United States,residing at Houston, Harris county. Texas. have invented a certain newand useful Improvement in Roller Earth-Boring Drill Cutters. of whichthe following is a full. clear, and exact description. such as willenable others skilled in the art to which it appertains to make and usethe same.

My invention relates to an improvement in roller earth boring drillcutters. and contemplates the prevention of mud and slush getting to thebearings of said cutters during that operation.

In the use of roller earth boring drills in the operation of drillingwells. especial-1y deep wells for oil, gas, sulphur. etc., the

drill is secured to the lower end of a hollow drill stem, and is rotatedat the bottom of the well, the roller cutters acting to cut away therock. The cuttings thus disintegrated by the bit are washed away andcarried to the surface by a stream of flushing fluid which is pumpeddown through the drill stem and the bit against the cutters. and flowsup outside of the drill stem in the well to the surface, carrying thecuttings in suspension therein. The flushing fluid which is used isordinarily a thick mud, and in most of the fields, this mud carries withit a considerable quantity of sand and grit in suspension therein. Dueto the heavy static ressure of the fluid in the hole, the mu tends to beforced inwardly around the bearings of the cutters, and causes excessivewear upon the bearings thereof.

The bearings are, under ordinary circumstances, lubricated by a forcefeed lubricator operated by the pressure of the fluid which is pumpeddown through the drill stem. The lubricant is forced to the bearings ofthe cutters through oil ducts in the head of the bit and the pin uponwhich the cutters are mounted. It is found, however, that while the bitis being lowered into the well the pumps are not operated, and as aresult the back pressure of the fluid in the well will force the mud inaround the bearings and fill the small spaces and chambers in theinterior of the cutter and the oil duct in the bit. When the pumps arestarted in the operation of the bit, the oil is forced downwardlyagainst this and the bit will operate for a considerable time with mudonly as a lubricant, and. even when the lubricant begins to flow, it isalmost impossible to eliminate entirely the sand and grit which hasworked in around the bearings.

It is the object of my invention to provide' a means to prevent the. mudfrom working into the oil ducts in the drill during the period-when thedrill is being lowered into the hole.

It is another object to provide a valve in the oil duct for the purposedescribed which may be located in the bushing of the cutter at a pointwhere the entrance of the mud may be most effectively prevented.

Other objects and advantages of the invention will more clearly appearin the specification which follows. Referring to the drawing herewith,wherein a preferred embodiment of my invention is disclosed. Fig. 1 Is acentral longitudinal section through a rock drill cutter showing theaplication of my invention thereto: Fig. 2 1s a .broken, enlarged detailthrough the valve employed; and F ig. 3 is a top plan view of the valveplate itself.

In the drawing I have shown my invcn-.

tion applied to a cutter for a rock drill bit of well knownconstruction. such as shown in the patent to Hughes. No. 979.496.granted December 27, 1910. In this draw ing, the head of the drill isshown at 1. The head has an outwardly projecting pin 2 to support thecutter. This pin is of large diameter adjacent to the head. and threadedfor attachment to the bushing 3 for the cutter. The outer end of the pin2 is reduced in diameter at 4 and is adapted to fit within the forwardend of the bushing 3.

The bushing 3 is a proximately frustoconical in shape, and ms a reducedshank 5. where it is secured to the cutter pin 2. The reduced shankprovides a space to receive the locking ring 6. by means of which thecutter 7 is retained upon the bushing. This construction is old in theart as shown in the patent referred to and forms no part of myinvention.

The outer surface of the cutter is provided with cutting teeth 8 bymeans of which the rock is disintegrated.

It will be noted that the bearing surface, where the cutter rotates uponthe bushing. provides a very slight passage along the base of the cutterand up around the surpoint there is ordinarily a small chamber 10 cmwhich the lubricant passes through a duct 11 to the outer surface of thebushing. In the forward end of the bushing I have formed a cylindricalrecess or valve chamber 12. In the lower end of this chamber,

and covering the opening from said duct 11, I place a valve plate 13.The form of this plate is shown particularly in Fig. 3. It is circularat the central portion, with a plurality of radial arms thereon whichfit against the inner surface of the recess. This plate is heldresiliently over the opening by means of a spiral spring 14. This springbears at its outer end against a nut or set screw 15having a centralopening 16 therein. This valve serves to prevent the passage of fluidinwardly toward the lubricator duct and to allow the passagetherethrough of lubricant in an obvious manner.

In the use of a cutter with the valve arrangement thereon, the bushingis covered with a thick coating of viscous lubricating oil and is thenplaced within the cutter and the locking ring secured in place. In thiswa the slight space between the cutter and loching ring outside thebushing is entirely filled with the thick oil. The cutter is thenscrewed upon the pin and the bit is introduced into the hole. The heavypressure of the mud upon the bearings, while the bit is being submergedin the mud in the well, will find no assage to the bearings. There willbe no ciance for the lubricant on the surface of the bushing to beforced back into the oil duct and into the air chambers about the cutterpin because of the;valve 13. By placing the valve in the end of-thebushing 1n this manner, a most effective means is provided to preventthe entrance of mud about the bearings in any manner. It iscomparatively easy to completely fill the space about the bushing withlubricant, but when it is attempted to fill the oil ducts and airchambers within the bushing with lubricant, it is found that it cannotbe done efiectively, and, even when attempted, the pressure of the mudin the hole will force the lubricant not only in exhausted with verylittle wear on the bushing; of the cutters themselves.

aving thus described my invention, what I claim as new and desire toprotect by Letters Patent is:

1. In a roller drill, a head. a cutter pin thereon, a bushing fittingover the end of said pin, a rotatable cutter on said bushing, acylindrical recess in the end of said bushing, an oil duct through saidhead, said pin, and said bushing, and terminating in said recess, avalve plate in said recess and means to hold said plate resiliently overthe end of said duct.

2. In a roller drill, a head, a cutter pin thereon, a bushing fittingover the end of said pin and screwed thereon, a cutter enclosing saidbushing, a lubricating ductin said head, said pin and said bushlng, arecess in said bushing at the end of said duct, an outwardly openingvalve in said recess, and means to hold said valve in position.

3. In a cutter for roller drills,-a supporting pin having an oil ducttherein, a bushing on said pin, a cutter enclosing said bushing, a valvechamber in said bushin at the "end of said oil duct and connectetherewith, a valve therein, a spring holding said valve in position, anda perforated plug in said chamber in the manner described.

4. In a cutter for roller drills, an approximately frusto-conical shapedbushing, 11. valve chamber formed in the outer apex thereof and havingan oil passage leading thereto, a valve in said chamber, and means .tohold said valve resiliently in position over said passage.

5. In a cutter for roller drills, a cutter pin, a bushin thereon, an oilduct in said pin and said ushing, an outwardly openin valve in saidbushing adapted to close said duct, and a cutter on said bushing.

In testimony whereof, I hereunto affix my signature, this the 31st dayof March, A. D 1923.

FLOYD L. SCOTT.

